Scanning of a color film images is commonly accomplished by projecting the image through a lens, dividing it into red, green and blue light using beam splitters and focusing the resultant individual color images on to three separate linear sensor arrays, typically of the charge coupled device (CCD) type. This approach, while effective, has several disadvantages. For example, it requires critical optical alignment between the components of the optical system and there are significant cost involved with the critical alignment procedures as well as with provision of the components involved, such as the lens, beam splitters and related mounting hardware. In addition, the space needed for the optical arrangement produces a bulky design not suited to desired compact scanner designs.
An improved scanner arrangement not requiring beam splitters and separate linear imaging arrays is disclosed in U.S. Pat. No. 4,278,995 commonly assigned to the assignee of the present invention. In this arrangement, the color image is focussed by means of a conventional lens optical system onto a trilinear CCD array in which the linear arrays individually responsive to red, green and blue are positioned side-by-side in a common plane. The signal outputs of two of the three arrays are respectively time delayed by appropriate amounts to cause the red, green and blue values corresponding to a common image pixel to be applied simultaneously to the ensuing video signal processing circuits. In a later U.S. Pat. No. 4,675,727, a similar trilinear arrangement is employed for document scanning but with the conventional lens arrangement replaced by a SELFOC lens arrangement in which individual microscopic lens elements are aligned with photosites on the CCD arrays to focus the image onto the arrays. Arrangements of these types represented improvements over the beam splitter approach but still required costly optical focussing systems with critical alignment considerations for satisfactory operation.
It is therefore an object of the present invention to provide color film scanning apparatus which avoids the disadvantages of prior known scanning apparatus.
It is a further object of the invention to provide color film scanning apparatus that avoids the need for costly and space consuming beam splitters and optical focussing systems.
It is yet another object of the invention to provide color film scanning apparatus that does not require the provision and maintenance of critical alignment techniques for proper operation.